Methods and compositions for prevention of fouling in caustic towers

ABSTRACT

Provided are methods and compositions for inhibiting carbonyl based fouling materials of basic wash systems. Said methods comprise contacting the hydrocarbon stream that is or will be subjected to said wash systems with water soluble or water dispersible copolymers. Said copolymers comprise repeat units of ethylenically unsaturated monomers such as acrylic acid with other repeat units such as alkyl acrylates, allyl ethers, ethoxylated allyl repeat units, etc. In other embodiments, a third repeat unit is present and may comprise a hydrophobic moiety such as a styrene repeat unit.

FIELD OF INVENTION

The invention relates to methods and compositions for inhibiting theformation of fouling deposits in basic wash systems of the type adaptedto scrub impurities, such as those that may be formed via aldolcondensation reactions, from liquid or gas phase hydrocarbonaceousstreams.

BACKGROUND OF THE INVENTION

Olefinic compounds such as ethylene, propylene, butylene, and amylenecan be formed from methanol to olefin (MTO) or various pyrolyticcracking processes. In these processes, a variety of carbonyl compoundssuch as aldehydes and ketones are often formed. Typically, the carbonylcompounds are found in the gas stream in about 1 to 200 parts permillion (ppm) by weight relative to the hydrocarbon stream withconcentrations of more than 1,000 ppm sometimes encountered due to theparticular feedstock and reactor operation parameter employed for thereactions.

The hydrocarbon product stream formed via cracking or MTO processes iscooled and sometimes compressed. The product gas stream may be passedthrough a basic wash system (pH>7) to remove acidic components such ashydrogen sulfide and carbon dioxide. In many cases, the carbonylcompounds present, such as the aldehydes, will undergo polymerization toform condensation polymers known as aldol polymers or red oil. Thesealdol polymers or red oil possess low solubility in the alkaline washand the hydrocarbon media and can deposit on wash tower tray conduitsand other internal surfaces of the process equipment leading to foulingand eventual plugging. These deposits can restrict flow through theequipment and can cause undesirable pressure drops, resulting indecreased process throughput, increased operating costs, and unit shutdown for periodic cleaning.

The basic wash systems in which treatment is required to inhibit suchpolymer based fouling include amine acid gas scrubber, such as MEA, DEA,isopropyl amine, butyl amine, etc., and caustic wash systems.

Generally, the basic washing entails contacting the gaseous olefins withan aqueous basic solution in a wash tower to remove hydrogen sulfide,carbon dioxide, and other oxygenated compounds therefrom. The basicwashing is particularly appropriate for the basic washing process whichfollows the pyrolytic cracking of such hydrocarbons as ethane, propane,butane, naphtha, and mixtures thereof to produce the correspondinggaseous ethylene, propylene, butadiene, and the like, or follows the MTOproduction process containing the carbonyl and other contaminants.

SUMMARY OF THE INVENTION

In one embodiment of the invention, methods are provided for inhibitingthe formation of fouling materials comprising contacting a hydrocarbonmedia containing aldehyde compounds with an antifoulant. The hydrocarbonmedia is treated in a basic wash system. The antifoulant may comprise apolymer having repeat units characterized by the formula

wherein a must be present, b or c or b+c is present and d may or may notbe present; E is a repeat unit remaining after polymerization of anethylenically unsaturated compound and can be, for example, (meth)acrylic acid or (meth) acrylamide; each R₁ is independently chosen fromH or lower (C₁-C₄) alkyl; R₂ is a hydroxy substituted alkyl or alkylenemoiety having from about 1-6 carbon atoms, X is an anionic radicalselected from the group consisting of SO₃, OSO₃, PO₃OPO₃ or COO; M isone or more hydrogens or any water soluble cationic moiety thatcounterbalances the valence of the anionic radical X and can be Ca, Na,K, NH₄, etc.; F is an ethylenically unsaturated hydrophobic moiety suchas styrene and its derivatives, acrylonitrile, olefin with (C₁-C₁₈)alkyl group, alkyl (meth) acrylate; Q in repeat unit c is chosen fromC₁-C₃ alkylene or carbonyl, m is 0 or 1, R₃ is CH₂—CH—O_(n) orCH₂—CHCH₃—O_(n) wherein n is from 1 to about 100 or R₃ is CH₂—CHOH orCH₂—CH—(OH)—CH₂; R₄ is H, OH, SO₃M, OSO₃M, PO₃M, OPO₃M, or CO₂M; withthe proviso that when d is present it is present in an amount of0.01-0.8 moles based on 1 mole of a; either b or c, or both b+c (whenboth are present) are present in a molar ratio of a:b or a:c or a:(b+c)of 0.1-100, or in some exemplary embodiments 1-10.

In certain embodiments, the polymeric antifoulant may comprise acopolymer of acrylic acid (AA) and allyl ether. In other embodiments ofthe invention, the polymeric foulant may be an acrylic acid (AA)allylhydroxylated alkyl ether, also referred to as 1-propane sulfonicacid, 2-hydroxy-3 (2-propenyl oxy) mono sodium salt (AHPSE).

The polymeric antifoulant may also be a terpolymer of AA/AHPSE/styreneor it may be, in certain embodiments, a copolymer of acrylic acid and anallyl polyethylene glycol ether. In some cases, the polymer may comprisea copolymer of acrylic acid with an ethoxylated allyl ether. In otherembodiments, the copolymer may comprise acrylic acid and lower alkylacrylates such as hydroxy substituted alkyl acrylates.

In another aspect of the invention, novel water soluble or waterdispersible polymer compositions are provided having the structure

E_(a)G_(z)F_(d)  Formula VI

wherein a, z, and d are all present; E is a repeat unit remainingafter polymerization of an ethylenically unsaturated compound, F is arepeat unit remaining after polymerization of an ethylenicallyunsaturated hydrophobic moiety; wherein the molar ratio of d:a is about0.1-0.8 moles of d:1 mole a; z is present in an amount of a:z of0.1-100, 1-10 moles a per 1 mole z and in some embodiments is present inan amount of 1-10 moles of a per mole z; G is a repeat unit chosenfrom VIa, VIb, VIc, or VId or mixtures thereof, wherein VIa is

VIb is

wherein R₁ is H or lower (C₁-C₄) alkyl, R₂ is a hydroxy substitutedalkyl or alkylene moiety having from about 1-6 carbon atoms, X is ananionic radical selected from the group consisting of SO₃, OSO₃, PO₃,OPO₃, or COO; M is H or hydrogens or any water soluble cationic moietythat counterbalances the valence of the anionic radical X; Q is chosenfrom C₁-C₃ alkylene or carbonyl, m is 0 or 1; R₃ isCH₂—CH₂—O_(n); —CH₂CHCH₃O_(n) wherein n=1 to 100; or R₃ ishydroxylated lower (C₁-C₄) alkylene; and R_(4i), is H, OH, SO₃M, OSO₃M,PO₃M, OPO₃M, or CO₂M;

VIc is

wherein R₁ is as defined above, R₅ is NH or O; R₆ is lower (C₁-C₄) alkylor alkylene or lower (C₁-C₄) hydroxy substituted alkyl or alkylene; Xand M are as defined above; and VId is

wherein R₇ is CH₂ or benzyl, and X and M are defined above.

In further aspects of the invention, novel water soluble terpolymercompositions are provided that comprise acrylic acid or acrylic acidsalt repeat units, a hydrophobic repeat unit such as styrene and itsderivatives, acrylonitrile, olefin with (C₁-C₁₈) alkyl group, alkyl(meth) acrylate, and a third repeat unit selected from the groupconsisting acrylamide repeat units, allyl ether repeat units, loweralkyl (C₁-C₄) acrylate repeat units, ethoxylated or propoxylated allylrepeat units, allyl polyethylene glycol ether repeat units, sulfonatedstyrene repeat units, and allyl sulfonic acid repeat units. Terpolymerswherein the hydrophobic monomeric repeat unit comprises styrene may bementioned as exemplary.

BRIEF DESCRIPTION OF THE DRAWING

The invention is further described in connection with the drawingswherein:

FIG. 1 is a microphotograph of filter cakes resulting from candidateantifoulant treatments as referred to in Example 3.

DETAILED DESCRIPTION

In one aspect of the invention, methods and compositions are provided toinhibit the formation of polymeric based fouling deposits during thebasic washing of hydrocarbons contaminated with carbonyl compounds whichlead to the formation of undesirable insoluble polymer contaminants. Inone embodiment, the antifoulant compound is a polymer having the FormulaI

wherein a must be present and either b or c or both b and c are present;d may or may not be present. In one embodiment, d is present. E is arepeat unit remaining after polymerization of an ethylenicallyunsaturated compound including carboxylic acids such as acrylic acid,sulfonic acid, phosphonic acid, or amide of such acid or mixturesthereof; E can be for example (meth) acrylic acid or (meth) acrylamide;each R₁ is independently chosen from H or lower (C₁-C₄) alkyl. R₂ is ahydroxy substituted alkyl or alkylene moiety having from about 1-6carbon atoms, X is an anionic radical selected from the group consistingof SO₃, OSO₃, PO₃, OPO₃, or COO; M is one or more hydrogens or any watersoluble cationic moiety that counterbalances the valence of the anionicradical X including but not limited to Na, K, Ca, or NH₄; F is anethylenically unsaturated hydrophobic moiety such as styrene, and itsderivatives, acrylonitrile, olefin with (C₁-C₁₈) alkyl group, alkyl(meth) acrylate.

Q in repeat unit c is chosen from C₁-C₃ alkylene or carbonyl; m is 0 or1 meaning that O may or may not be present, R₃ is CH₂—CH₂—O_(n)CH₂—CHCH₃—O_(n) wherein n ranges from about 1 to 100, including 1 to20, or R₃ is hydroxylated lower (C₁-C₄) alkylene such as CH₂—CH(OH) orCH₂—CH(OH)—CH₂; R₄ is H, OH, SO₃M, OSO₃M, PO₃M, OPO₃M, CO₂M or mixturesthereof with M being previously defined.

In Formula I above, when d is present, it is present in an amount ofabout 0.01-0.8 moles based on 1 mole of a. Either b or c, or both b or cif both are present, are present in a monomer ratio of a:b or a:c ora:(b+c) of 0.1-100, including 1-10. The molecular weight of polymers asset forth in Formula I is not critical as long as the polymer is watersoluble or water dispersible. In some embodiments, the molecular weightcan range from about 500-50,000 (Mn).

Exemplary polymers that may be used to inhibit fouling inhydrocarbonaceous media containing carbonyl compounds such as aldehydesinclude acrylic acid/allyl ether copolymers such as acrylic acid/allylhydroxylated alkyl copolymers and water soluble salt forms thereof suchas acrylic acid/1-propane sulfonic acid, 2 hydroxy-3(2-propenyl oxy)mono sodium salt also referred sometimes to as acrylic acid/allylhydroxypropyl sulfonate ether (AHPSE). Additionally, terpolymerscomprising acrylic acid/AHPSE/and styrene repeat units can also bementioned.

Acrylic acid/ethoxylated allyl ethers such as those enumerated in U.S.Pat. No. 7,094,852 can also be mentioned as exemplary. These includeacrylic acid/allylpolyethoxylated copolymers such as acrylicacid/allylpolyethoxy (10) sulfate (APES) and others. Also, acrylicacid/allyl polyethylene glycol ethers such as those set forth in U.S.Pat. No. 6,641,754 are noteworthy. One particular terpolymer of interestis a terpolymer of acrylic acid/AHPSE/and ammonium allyl polyethoxy (10)sulfate.

Other exemplary polymers can include water soluble or water dispersibleacrylic acid/hydroxylated alkyl acrylates such as acrylic acid/2hydroxypropylacrylate copolymers. Certain of the exemplary polymers areshown in Formula II-V following:

The copolymer shown in Formula II may be referred to as AA/AHPSE (asherein used AA denotes acrylic acid and/or its various water solublesalt forms), and AHPSE has been previously referred to.

The terpolymer shown in Formula III may be referred to asAA/AHPSE/styrene.

This may be referred to as AA/AHPSE/allylpolyethoxy(10) sulfate (APES).

AA/AHP SE/APES/Styrene

The antifoulant polymers may be fed to the basic (pH>7) wash toweritself or to input or recycle lines in communication with the washtower. In some cases, the antifoulant is dosed into the caustic solutionfeed or recycle lines that are in fluid communication with the washtower. Typically, the antifoulant polymers are fed to the hydrocarbonstream (charge gas) in an amount of 1-2,000 ppm by weight relative tothe hydrocarbon stream. In other embodiments, the antifoulants are fedin an amount of about 1-1,000 ppm. In one embodiment, the feed rate maybe from about (0.01-100)X of the antifoulant wherein X is the molarconcentration of aldehyde or ketone in the charge gas.

In Formulae III and IV, a, b, and c are, independently, zero or apositive integer such that the molecular weight of the molecule is lessthan about 500,000 Daltons, such as from 500-500,000 Daltons. In FormulaV, a, b, c, and d, are independently zero or positive integers such thatthe molecular weight of the molecule is less than about 500,000 Daltons.

In some aspects of the invention, the antifoulant is conjointly usedwith other carbonyl scavengers which can include alcohol amines such astriisopropanolamine, diglycolamine, aminomethylpropanol, N,N-diethylethanolamine, monoisopropanolamine, monoethanolamine,diethanolamine, triethanolamine, dimethylaminoethanol, and etc.; alkylamines, such as phenothiazine, diazacyclohexane,N—N-dimethyldodecylamine, N,N′-bis(1-methylpropyl)-1,4-phenylenediamine,aminoethylpiperazine, 1,2-dianilinoethane, diethylenetriamine and etc.;keto-amines, such as triacetonamine; amino acids, such as 6 aminocaproic acid; hydrazide compounds, such as 1,2-diformylhydrazine,carbohydrazide, N-methyl-hydrazide, oxalyl dihydrazide,chlorobenzhydrazide, aminobenzhydrazide, benzoic hydrazide, and etc.;hydroxylamine compounds, such as N,N-diethylhydroxylamine, isopropylhydroxylamine, hydroxylamine sulfate, N,N-dialkylhydroxylamine, andetc.; reducing sugars, hydroxybenzenes, acetoacetate ester compounds,lactams, oxidizers, such as hydroperoxide, peroxyester, percarbonatecompounds and etc.; and reducer, such as sodium borohydride, sodium(bi)sulfite and etc. These additional compounds may be present in anamount of about 1 to about 2,000 ppm by weight relative to thehydrocarbon stream.

In another aspect of the invention, novel water soluble or waterdispersible polymers are provided that are useful as deposit control,scale inhibition and anti-foulant treatments in hydrocarbon media. As anexample, these polymers may be used to inhibit carbonyl based polymerdeposits that may otherwise form in basic washing systems employed inMTO and olefin cracking processes. The antifoulant polymers generallyhave the Formula VI

E_(a)G_(z)F_(d)  Formula VI

wherein a, z, and d are all present. E and F are as previouslydefined in conjunction with Formula I. G is VIa, VIb, VIc, or VId ormixtures thereof, or G is either or both of the repeat unit moietiesof b and c as set forth in Formula I, wherein

VIa is

VIb is

wherein R₁ is H or lower (C₁-C₄) alkyl, R₂ is a hydroxy substitutedalkyl or alkylene moiety having from about 1-6 carbon atoms, X is ananionic radical selected from the group consisting of SO₃, OSO₃, PO₃,OPO₃, or COO; M is H or hydrogens or any water soluble cationic moietythat counterbalances the valence of the anionic radical X; Q is chosenfrom C₁-C₃ alkylene or carbonyl, m is 0 or 1; R₃ is CH₂—CH₂—O_(n);—CH₂CHCH₃O_(n) wherein n=1 to 100; or R₃ is hydroxylated lower (C₁-C₄)alkylene; and R₄ is H, OH, SO₃M, OSO₃M, PO₃M, OPO₃M, or CO₂M or mixturesthereof with M being as previously defined;

VIc is

wherein R₁ is as defined above, R₅ is NH or O; R₆ is lower (C₁-C₄) alkylor alkylene or lower (C₁-C₄) hydroxy substituted alkyl or alkylene; Xand M are as defined above; and VId is

wherein R₇ is CH₂ or benzyl, and X and M are defined above.

In Formula VI, the molar ratio of d:a is about 0.1-0.8 moles of d per 1mole a; z is present in an amount of a:z of 0.1-100 moles a per 1 mole zwith certain embodiments having 1-10 moles a per 1 mole z.

Exemplary polymers in accordance with Formula VI include acrylic acid(AA)/2-acryloylamino-2-methyl-1-propanesulfonic acid (AMPS)/styreneterpolymers (i.e., Formulae VI and VIc) wherein E is AA, R₅ is NH,R₆=2-methylpropane, and X is SO₃ ⁻; F is styrene. Additionally, FormulaVI terpolymers of AA/allysulfonic acid/styrene can be noted wherein R₇in Formula VId is CH₂ with X being SO₃ ⁻. Also, in some embodiments, R₇can comprise a benzyl moiety with X being SO₃ ⁻, namely AA/sulfonatedstyrene/styrene terpolymers.

Further, other terpolymeric combinations within the ambit of Figure VIinclude AA/AHPSE/styrene terpolymers, AA/lower alkyl (C₁-C₄)acrylate/styrene terpolymers, AA/hydroxylated alkyl (C₁-C₄)acrylate/styrene terpolymers, AA/allyl polyethylene glycol (PEG)ether/styrene terpolymers; AA/allyl polyethyoxy sulfate (APES)/styreneterpolymers and AA/PEG allyl ether/APES/styrene polymers.

The polymers of the invention can be prepared via radical chain additionpolymerization of the requisite monomers. The reaction may proceed, forexample, under conventional solution polymerization techniques. Therequisite monomers may be mixed with water and alcohol. Polymerizationinitiators such as the persulfate initiators, peroxide initiators, etc.,may be employed. The resulting copolymers, terpolymers, quad polymers,etc. (at least four monomeric repeat units) may be isolated by wellknown techniques such as distillation, etc., or the polymer may simplybe used in aqueous solution.

For example, a terpolymer in accordance with Formula III can be preparedas follows:

1. Charge initial 97.7 g (sodium 1-allyloxy 2-hydroxy propyl sulfonate)and 50 g DI water into the reactor and set up the reactor

2. Record reactor weight

3. Sparge with N₂ for 10 minutes

4. Switch to a nitrogen blanket and heat to 90° C.

5. Start a simultaneous co-feed of the following reagents

-   -   39 g Acrylic Acid over 150 minutes    -   5 g Styrene over 60 minutes    -   25 g Sodium persulfate (5%) over 150 minutes

6. After feed, hold at 90° C. for 90 minutes

7. Cool to room temperature and add caustic solution (50% NaOH solution)and dilution water

8. Measure reactor weight and solid content.

In some aspects of the invention, a water soluble terpolymer compositionis provided that comprises: i) acrylic acid or acrylic acid salt repeatunits, ii) a hydrophobic repeat unit such as styrene repeat units, and athird repeat unit iii). The third repeat unit may be selected from thegroup consisting of acrylamide repeat units, allyl ether repeat units,lower alkyl (C₁-C₄) acrylate repeat units, ethoxylated or protoxylatedallyl repeat units, allyl polyethylene glycol ether repeat units,sulfonated styrene repeat units, and allyl sulfonic acid repeat units.

In some cases, the third repeat unit may be 2-acrylamido-2-methyl-1propane sulfonic acid (AMPS). In other cases, the third repeat unit maybe allyl hydroxypropyl sulfonate ether (AHPSE). Still, in other aspects,the third repeat unit may comprise allylpolyethoxy sulfonate (APES).Additionally, the third repeat unit may, in some aspects of theinvention, comprise hydroxypropyl acrylate (HPA). In other embodiments,this third repeat unit may comprise AHPSE, and a fourth repeat unit maybe present. This fourth repeat unit may comprise APES.

These terpolymer comprising repeat units i), ii), and iii) may comprisemonomeric repeat units of about 0.01-0.8 moles ii) per mole of i). Therepeat unit iii) may be present in an amount of about 0.1-100, including1-10 moles i) per mole of iii). Molecular weight of these polymers mayrange from about 500-500,000 (Mn).

The invention will be described in conjunction with the followingspecific examples which are to be regarded as illustrative and not asrestricting the scope of the invention.

EXAMPLES Example 1

In order to simulate carbonyl compound fouling in caustic towers and toevaluate the dispersion capability and fouling inhibition of candidatecompounds, the following procedure was employed.

TABLE 1 Components of simulated carbonyl compound fouling and treatmentComponents Concentration NaOH 10% (w/w) Dispersant/inhibitor 0-1000 ppmAcetaldehyde 2000 ppm25 ml 10% NaOH and no dispersant (blank)/1000 ppm dispersant werecharged into a 30 ml glass bottle. The bottle was capped and thesolution was mixed. Then 2000 ppm aldehyde was dosed into the bottlesand mixed after the bottle had been capped tightly. After that, themixture was incubated in a water bath at 50° C. for 24 hours. Finally,the mixture appearance of the bottle was recorded immediately when beingtaken out of the water bath without shaking. Thus, the sample untreatedand samples tested with the candidates listed in Table 2 were tested.Results are shown in Table 3.

Dispersant/inhibitor candidates were selected. Some of these includedknown dispersant/inhibitors that are commonly used to control carbonylbased fouling. These are designated in Table 2 with the prefix “C”(comparative). Dispersant inhibitor compounds in accordance with theinvention are denoted by the prefix “N”.

TABLE 2 Candidates of inhibitor and dispersant Candidate Chemical C1 30%Hydroxylamine sulfate C2 45% Naphthalene sulfonate formaldehydecondensate C3 Poly(AA/AMPS) (43% solid) C4 PAA (50% solid) C5 PMA (50%solid) C6 Sodium Ligninsulfonate (45% solid) N1 Chemical with Formula II(37% solid) N2 Chemical with Formula III (37% solid) N3 Chemical withFormula IV (50% solid) N4 Chemical with Formula V (51% solid)AA=acrylic acid or salt thereof; poly (AA/AMPS)=poly (acrylicacid/2-acrylamido-2-methylpropane sulfonic acid); PAA=polyacrylic acid,PMA=poly maleic acid; N₁=poly (acrylic acid/allyl 2-hydroxypropylsulfonate ether (AA/AHPSE)); N₂=poly (acrylic acid/AHPSE/styrene)terpolymer; N3=poly (AA/AHPSE/allylpolyethoxy (10) sulfate (APES));N4=poly (AA/AHPSE/APES/styrene).

Carbonyl compound fouling dispersion capability of the commondispersants in water system was studied. The carbonyl compound foulingwas simulated and treated as Example 1. The dispersion performance ofthe candidates in Table 2 was studied under 1000 ppm product dosage byweight relative to the total solution. Table 3 shows the test results.From the appearance, we can conclude that the C1, C3, C4 and C5 did notshow any dispersion capability to the carbonyl compound fouling at 1000ppm dosage. C2 and C6 possessed some dispersion capability to the formedfouling. The sample treated with N1 resulted in a homogeneous suspensionwith a little precipitation, no flocs observed. This indicates that N1possesses good dispersion capability to the polymeric fouling caused bycarbonyl compound, such as aldehyde in caustic tower. N2 showed the bestdispersion performance without any flocs or precipitation. Thehydrophobic monomer in N2 enhances its dispersion capability.

TABLE 3 Carbonyl compound fouling dispersion test result CandidateResult Blank Severe flocs C1 Severe flocs C2 Flocs C3 Severe flocs C4Severe flocs C5 Severe flocs C6 Moderate Flocs N1 Homogeneous suspensionwith a little precipation N2 Homogeneous suspension N3 Homogenoussuspension with a little precipitation N4 Homogenous suspension

Example 2

The carbonyl compound fouling dispersion performance of C2, N1 and N2was studied under dosage from 500 to 1000 ppm. The carbonyl compoundfouling was simulated and treated as Example 1. Table 4 lists the testresult. From the table, it can be observed that N2 showed the bestdispersion capability, 800 ppm dosage was enough to keep the foulingsuspension stable under lab static test condition.

TABLE 4 Carbonyl compound fouling dispersion V.S. dosage Treatmentreagent 500 ppm 800 ppm 1000 ppm C2 Severe flocs Flocs Flocs N1 Severeflocs Flocs Homogeneous suspension with a little precipation N2 FlocHomogeneous Homogeneous suspension suspension

Example 3

The dispersion capability was evaluated with a filtration method. Thecarbonyl compound fouling was simulated and treated by the proceduressimilar with Example 1. 200 ml 10% NaOH was charged into 500 ml glassbottle and no treatment (blank) and 1000 ppm treatment reagents,including C1, C2 and N2 were dosed into the bottles. The bottles werecapped and shaken. Then, 2000 ppm aldehyde was dosed into the abovesolution and mixed. After that, the mixture was incubated in water bathat 50° C. for 24 hours immediately. Finally, the bottle was taken out,mixed and then the suspension was filtrated with 0.8 μm fiberglassfilter. FIG. 1 shows the filter cakes of the fouling treated withcorresponding chemicals. It can be observed that there was no foulingsubstance kept on the surface of the filter after being treated with N2.It shows that the fouling particle size after being treated with N2 issmaller than 0.8 μm. This indicates N2 possesses excellent capability todisperse carbonyl compound fouling into small particles. This kind ofcapability can prevent the fouling to flocculate or precipitate, so toeliminate the jamming or blockage in the caustic tower tray or pipelinesduring MTO, ethylene or propylene production process.

While this invention has been described with respect to particularembodiments thereof, it is apparent that numerous other forms andmodifications of this invention will be obvious to those skilled in theart. The appended claims an this invention generally should be construedto cover all such obvious forms and modifications which are within thetrue spirit and scope of the present invention.

1. A method for inhibiting the formation of fouling materials comprisingcontacting a hydrocarbon stream containing carbonyl compounds with anantifoulant and treating said hydrocarbon stream with a basic wash,wherein said antifoulant comprises a polymer having repeat unitscharacterized by the formula

wherein a must be present, b or c or b+c is present and d may or may notbe present; E is a repeat unit remaining after polymerization of anethylenically unsaturated compound; each R₁ is independently chosen fromH or lower (C₁-C₄) alkyl; R₂ is a hydroxy substituted alkyl or alkylenemoiety having from about 1-6 carbon atoms, X is an anionic radicalselected from the group consisting of SO₃, OSO₃, PO₃OPO₃ or COO; M is Hor hydrogens or any water soluble cationic moiety that counterbalancesthe valence of the anionic radical X; F is an ethylenically unsaturatedhydrophobic moiety; Q in repeat unit c is chosen from C₁-C₃ alkylene orcarbonyl, m is 0 or 1, R₃ is CH₂—CH—O_(n) or CH₂—CH—CH₃—O_(n)wherein n is from 1 to about 100 or R₃ is CH₂—CHOH or CH₂—CH—(OH)—CH₂;R₄ is H, OH, SO₃M, OSO₃M, PO₃M, OPO₃M, or CO₂M; with the proviso thatwhen d is present it is present in an amount of 0.01-0.8 moles based on1 mole of a; either b or c, or both b+c (when both are present) arepresent in a molar ratio of a:b or a:c or a:(b+c) of 0.1-100.
 2. Themethod of claim 1, wherein about 1-2,000 ppm of said antifoulant isbrought into contact with said hydrocarbon stream, based upon 1 millionparts of said stream by weight.
 3. The method of claim 1, wherein saidpolymer is a copolymer of acrylic acid (AA) acid/allyl ether or(AA)/allyl hydroxylated alkyl ether.
 4. (canceled)
 5. The method ofclaim 1, wherein said polymer is a terpolymer of AA/AHP SE/styrene. 6.The method of claim 1, wherein said polymer is a copolymer ofAA/allylpolyethyleneglycol ether or AA/ethoxylated allyl ether.
 7. Themethod of claim 6, wherein said ethoxylated allyl ether isallylpolyethyoxy (10) sulfate.
 8. The method of claim 1, wherein saidpolymer is a terpolymer of AA/AHPSE/ammonium allylpolyethoxy (10)sulfate or a copolymer of AA/lower alkyl (C₁-C₄) acrylate.
 9. The methodof claim 8, wherein said lower alkyl (C₁-C₄) acrylate is an hydroxyalkyl acrylate.
 10. The method of claim 9, wherein said hydroxy alkylacrylate is 2 hydroxypropyl acrylate (HPA).
 11. The method of claim 1,wherein said polymer is a terpolymer of AA/HPA/AHP SE/styrene. 12.(canceled)
 13. The method of claim 1, wherein the antifoulant is addedto the hydrocarbon stream simultaneously with the base wash or is addedto the hydrocarbon stream in a hydrocarbon charge line to a basic washtower or is added to the hydrocarbon stream in an input line to orrecycle line from a basic wash tower, or a recycle line from a basicwash tower or to a caustic solution pipeline line.
 14. The method ofclaim 1, wherein said hydrocarbon stream is a methanol to olefin (MTO)process stream or a cracked hydrocarbon stream from the pyrolysis ofhydrocarbons.
 15. The method of claim 14, wherein the crackedhydrocarbon stream is from the pyrolysis of ethane, propane, butane,naphtha, or mixtures thereof.
 16. The method of claim 1, wherein thebasic wash has a pH greater than 7.0 and comprises sodium hydroxide,potassium hydroxide, sodium carbonate, sodium hydrocarbonate, potassiumhydrocarbonate, organic amine, or an alkanolamine.
 17. The methodaccording to claim 1, wherein the antifoulant further comprises anothercarbonyl scavenger, said another carbonyl scavenger comprises at leastone compound selected from the group consisting of alcohol amines, alkylamines, keto amines, amino acids, hydrazide compounds, hydroxylamines,reducing sugars, hydroxybenzenes, acetoacetate ester compounds, lactams,oxidizers, and reducers.
 18. (canceled)
 19. A water soluble or waterdispersible polymer composition having the structureE_(a)G_(z)F_(d)  Formula VI wherein a, z, and d are all present;E is a repeat unit remaining after polymerization of an ethylenicallyunsaturated compound, F is a repeat unit remaining afterpolymerization of an ethylenically unsaturated hydrophobic moiety;wherein the molar ratio of d:a is about 0.1-0.8 moles of d:1 mole a; zis present in an amount of a:z of 0.1-100 moles a per 1 mole z; G is arepeat unit chosen from VIa, VIb, VIc, or VId or mixtures thereof,wherein VIa is

VIb is

wherein R₁ is H or lower (C₁-C₄) alkyl, R₂ is a hydroxy substitutedalkyl or alkylene moiety having from about 1-6 carbon atoms, X is ananionic radical selected from the group consisting of SO₃, OSO₃, PO₃,OPO₃, or COO; M is H or hydrogens or any water soluble cationic moietythat counterbalances the valence of the anionic radical X; Q is chosenfrom C₁-C₃ alkylene or carbonyl, m is 0 or 1; R₃ is CH₂—CH₂—O_(n);—CH₂CHCH₃O_(n) wherein n=1 to 100; or R₃ is hydroxylated lower (C₁-C₄)alkylene; and R₄, is H, OH, SO₃M, OSO₃M, PO₃M, OPO₃M, or CO₂M; VIc is

wherein R₁ is as defined above, R₅ is NH or O; R₆ is lower (C₁-C₄) alkylor alkylene or lower (C₁-C₄) hydroxy substituted alkyl or alkylene; Xand M are as defined above; and VId is

wherein R₇ is CH₂ or benzyl, and X and M are defined above.
 20. Thepolymer composition as recited in claim 19, wherein E is acrylic acidor water soluble salt form thereof (AA).
 21. The polymer composition ofclaim 20, wherein F is styrene.
 22. The polymer composition of claim21, wherein G is VIc and R₅ is NH, or O; R₆ is 2-methyl-1-propane or 2hydroxypropyl, and X is SO₃.
 23. (canceled)
 24. The polymer compositionof claim 21, wherein G is VIa and R₂ is 2 hydroxypropyl and X is SO₃.25. The polymer composition of claim 21, wherein G is VIb and Q isCH₂, m=1; R₃ is CH₂—CH₂—O_(n) and R₄ is SO₃M.
 26. The polymercomposition of claim 21, wherein G is VIb and wherein Q=CH₂, m=O; R₃is CH₂CH₂—O_(n) and R₄ is OSO₃M.
 27. The polymer composition of claim21, wherein G comprises both VIa and VIb and wherein R₂ ishydroxypropyl; X is SO₃; Q is CH₂; m=O; R₃ is CH₂CH₂—O_(n) and R₄ isOSO₃M.
 28. The polymer composition of claim 21, wherein G is VId;wherein R₇ is benzyl or CH₂, and X is SO₃.
 29. (canceled)
 30. A watersoluble terpolymer composition comprising acrylic acid or acrylic acidsalt (AA) repeat units, hydrophobic monomeric repeat units, and a thirdrepeat unit selected from the group consisting of acrylamide repeatunits, allyl ether repeat units, lower alkyl (C₁-C₄) acrylate repeatunits, ethoxylated or propoxylated allyl repeat units, allylpolyethylene glycol ether repeat units, sulfonated styrene repeat units,and allyl sulfonic acid repeat units.
 31. The water soluble terpolymercomposition as recited in claim 30, wherein said hydrophobic monomericrepeat units comprise styrene.
 32. The water soluble terpolymercomposition as recited in claim 31, wherein said third repeat unit is2-acrylamido-2-methyl-1 propane sulfonic acid (AMPS), allyl hydroxypropyl sulfonate ether (AHPSE), allylpolyethoxy sulfonate (APES), orhydroxypropyl acrylate (HPA). 33-36. (canceled)